The overall purpose of the Breeding and Genotyping Core (BGC) is to provide the participating investigators with state-of-the art, efficient and reliable support for maintaining the myriad of mouse lines (wild type and genetically altered) associated with the proposed studies. The BGC will provide individual investigators with the necessary technical support, expertise, reagents, and equipment for comprehensive mouse breeding and maintenance; thereby promoting research into the mechanisms by which IL-13 mediates the pathogenesis of asthma. Numerous mouse strains (often identical or related) are key components of each of the Projects; therefore, a major objective of the centralized BGC is to promote not only cost effective service but also the development of an important resource to further interactions between the investigating groups. The three specific aims are designed to meet the goals and objectives of all of the members of the Program Project. In Aim I, we will provide a centralized mouse inventory. The BGC will maintain a central bank of all mouse lines associated with the Program Project. The mouse lines will be maintained in a common housing facility and thus provide a repository of regularly available mouse lines. The mouse lines and census will be available via a common computerized network. In Aim II, we will centralize mouse breeding. The BGC will breed the required mouse lines associated with the Program Project. The mouse lines, often derived from secondary crosses between mice derived from individual Project Leaders, will be maintained in a common housing facility. In Aim III, we will provide expertise in mouse breeding and genotyping. The BGC will provide expertise up-to-date technology concerning mouse genotyping and breeding techniques. Many of the mouse lines associated with this Program Project will be genotyped by similar techniques; thus, the BGC will provide the common reagents (e.g. oligonucleotides for PCR or DNA probes for Southern blots) and protocols for genotype assessment.